1. Field
Embodiments relate to an energy storage system (ESS) and a method thereof.
2. Description of the Related Art
In general, an electrical energy source (for example, an electrochemical battery and generator) has characteristics of a linear voltage source, and thus, always maintains a constant voltage regardless of characteristics of a load. Additionally, since there is only one operating point in such an electrical energy source, it always operates as a stable system under any input and output condition. That is, when an electrical energy source with a linear voltage source is used, desired operating conditions may be obtained regardless of load conditions.
However, as one example, a solar cell or a wind power generator is classified as a representative nonlinear voltage source having completely different electrical characteristics from the above-mentioned electrical energy source. Especially, since voltage and current change in the solar cell according to the weather, its operating point is always changed. Due to such a phenomenon, an unstable state such as excessive ripple and oscillation may occur in a system during power conversion. Accordingly, in order to obtain stable output power at a desired operating point, it is necessary to appropriately adjust an operating point according to a voltage and current of a solar cell.
Thus, a technique for adjusting an operating point of a nonlinear power generating system in order to generate the maximum power amount is referred to as a maximum power point tracking technique. Since the maximum power point tracking technique for allowing an operating point to track the maximum power point has a direct impact on the generation amount of a nonlinear power generating system, it is very important.